For an exhaust turbocharger, often used is a variable nozzle mechanism disposed between an exhaust-gas channel of a scroll shape formed in a turbine housing and a turbine wheel rotatably disposed at the center of the turbine housing. The variable nozzle mechanism controls a flow of exhaust gas that acts on the turbine wheel.
Such a variable nozzle mechanism includes a nozzle mount and a nozzle plate supported by a nozzle support so as to be spaced from each other, and a plurality of nozzle vanes rotatably supported between the nozzle mount and the nozzle plate. The vane angle of the nozzle vanes is varied to control the flow of exhaust gas flowing between the nozzle mount and the nozzle plate, thereby controlling the flow of the exhaust gas acting on the turbine wheel.
Patent Documents 1 and 2, for example, disclose an example of a variable-geometry exhaust turbine having the above variable nozzle mechanism.